Antibacterial stainless steel plate for refrigerator lining and preparation method of antibacterial stainless steel plate

Abstract

The invention relates to the field of stainless steel materials, in particular to an antibacterial stainless steel plate for a refrigerator lining and a preparation method of the antibacterial stainless steel plate. Firstly, stainless steel alloy powder is added, and the stainless steel plate is prepared. And then the stainless steel plate is sequentially subjected to polishing, ultrasonic cleaning, drying, laser etching and re-cleaning, and the pretreated stainless steel plate is obtained. Dipping the pretreated stainless steel plate in the mesoporous polydopamine dipping liquid, and carrying out a light-shielding reaction to obtain the antibacterial adhesion layer. And coating the polyurethane-acrylic acid antibacterial coating on the surface of the stainless steel plate, and carrying out photocuring to obtain a finished product. The finished product prepared by the method has good antibacterial ability, and the coating can be firmly attached to a matrix, so that the method has wide application prospects in the field of stainless steel materials.

Description

Technical Field

[0001] The invention relates to the field of stainless steel materials, in particular to an antibacterial stainless steel plate for refrigerator lining and a preparation method thereof. Background Art

[0002] In the modern home appliance industry, stainless steel refrigerator linings are playing a significant role due to their unique advantages. From a practical perspective, stainless steel boasts exceptional durability. As household appliances used for extended periods of time, refrigerators operate in a complex internal environment, exposed to a variety of food and beverage liquids. Stainless steel's strong corrosion resistance effectively protects against these liquids, ensuring the refrigerator lining remains rust-free and deform-free over extended use, significantly extending the refrigerator's lifespan. Furthermore, stainless steel's smooth surface makes it easy to clean; simply wipe with a damp cloth to remove stains, maintaining a clean and hygienic refrigerator interior and providing an ideal environment for food storage. Industrially, stainless steel is easily processed and formed, allowing for linings of various shapes and sizes to be tailored to refrigerator design requirements, improving production efficiency and reducing costs. Furthermore, stainless steel is recyclable, aligning with sustainable development and reducing environmental impact.

[0003] However, the refrigerator is a place for storing food. The internal environment is humid and the temperature is suitable, which makes it easy for bacteria to grow. If the stainless steel plate does not have good antibacterial properties, bacteria will multiply in large numbers on its surface and contaminate the stored food. Eating food contaminated by bacteria may cause various diseases and endanger human health. Therefore, it is necessary to provide a stainless steel plate with antibacterial properties, so as to effectively inhibit the growth and reproduction of bacteria, reduce the risk of food contamination, and provide consumers with a safe food storage environment. Generally speaking, preparing an antibacterial coating on the surface of a stainless steel plate is a commonly used technical means to improve the antibacterial performance, but in the humid environment of the refrigerator, the coating is prone to falling off. This will not only affect the appearance of the refrigerator lining, making the refrigerator look old and unsightly, but also reduce the corrosion resistance of the stainless steel plate and shorten its service life. Therefore, it is necessary to improve the adhesion strength of the surface coating to ensure that the coating is firmly attached to the surface of the stainless steel plate for a long time and continues to play its due role.

[0004] In order to overcome the defects of the prior art, the present invention provides an antibacterial stainless steel plate for refrigerator lining and a preparation method thereof. Summary of the Invention

[0005] The object of the present invention is to provide an antibacterial stainless steel plate for refrigerator lining and a preparation method thereof, so as to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A preparation method of an antibacterial stainless steel plate for a refrigerator inner liner, comprising the following steps:

[0008] Step 1: Encapsulate and weld, forge, hot-roll, and perform shaping processing on the stainless steel alloy powder in sequence to obtain a stainless steel plate; then polish, ultrasonically clean, dry, laser etch, and clean again the stainless steel plate to obtain a pretreated stainless steel plate;

[0009] Step 2: Add mesoporous polydopamine nanoparticles to a Tris-HCl buffer solution with a pH of 8.5 - 9.0 to obtain a mesoporous polydopamine impregnating solution with a concentration of 3 - 5 mg / mL; then immerse the pretreated stainless steel plate in the mesoporous polydopamine impregnating solution, and react in the dark at 25 - 30 °C for 25 - 30 h to obtain an antibacterial adhesion layer;

[0010] Step 3: Under a nitrogen atmosphere, mix polypropylene glycol and polycaprolactone diol, stir at 55 - 60 °C for 20 - 30 min, then add isophorone diisocyanate and dibutyltin dilaurate, raise the temperature to 90 - 95 °C and continue stirring and reacting for 2.0 - 2.5 h, then cool down to 45 - 50 °C, and add a capping agent, 2-hydroxyethyl methacrylate, and continue reacting for 2 - 3 h to obtain vinyl-capped polyurethane; then mix vinyl-capped polyurethane, acrylic acid-modified chitosan, acrylic acid-modified tannic acid, and acrylated quaternary ammonium salt, stir evenly, add a photoinitiator, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and stir in the dark for 10 - 20 min to obtain a polyurethane-acrylic antibacterial coating; coat the polyurethane-acrylic antibacterial coating on the surface of the stainless steel plate obtained in Step 2, and perform photocuring at a wavelength of 250 - 260 nm for 5 - 7 min to obtain an antibacterial layer, which is the finished product.

[0011] Preferably, in Step 1, the laser etching parameters are: the scanning power is 15 - 20 W, the scanning speed is 250 - 350 mm / s, and the scanning spacing is 35 - 40 μm.

[0012] Preferably, in Step 1, the component contents of the stainless steel alloy powder are: by mass fraction, C: 0.01 - 0.08%, B: 0.5 - 1.5%, Si: 0.5 - 0.7%, Mn 1.0 - 1.5%, P: 0.0025 - 0.035%, S: 0.020 - 0.025%, Ni: 12.0 - 15.0%, Cr: 18.0 - 20.0%, N: 0.05 - 0.07%, O: 0.003 - 0.004%, and the balance is Fe and unavoidable impurities.

[0013] Preferably, in step two, the preparation process of the mesoporous polydopamine nanoparticles is as follows: Pluronic F-127 and 1,3,5-trimethylbenzene are sequentially added to the ethanol aqueous solution. After ultrasonic dispersion to obtain an emulsion, magnetic stirring is carried out for 30 - 40 min. Then, Tris-HCl aqueous solution and dopamine hydrochloride are sequentially added, and the pH is adjusted to 8.5 - 8.7. The reaction is carried out in the dark at 25 - 30 °C for 25 - 30 h. After the reaction is completed, the solid nanoparticles are collected at 3 - 5 °C, and then ultrasonically cleaned, centrifugally collected, washed with deionized water, and freeze-dried to obtain the mesoporous polydopamine nanoparticles.

[0014] Preferably, the reaction mass ratio of Pluronic F-127, 1,3,5-trimethylbenzene, Tris-HCl, and dopamine hydrochloride is (37 - 40):36:9:6.

[0015] Preferably, in step three, when preparing the vinyl-terminated polyurethane, the reaction mass ratio of polypropylene glycol, polycaprolactone diol, isophorone diisocyanate, and 2-hydroxyethyl methacrylate is 3:(1.0 - 1.6):2:1.

[0016] Preferably, in step three, the content of each component of the polyurethane-acrylic antibacterial coating is as follows: by mass fraction, 60 - 70% vinyl-terminated polyurethane, 15 - 20% acrylic acid-modified chitosan, 10 - 15% acrylated quaternary ammonium salt, 6 - 10% acrylic acid-modified tannic acid, and the balance is the photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone; the coating thickness is 20 - 30 μm.

[0017] Preferably, the preparation process of the acrylic acid-modified chitosan is as follows: Chitosan and triethylamine are added to tetrahydrofuran. After sufficient stirring, glycidyl methacrylate is sequentially added dropwise. After the addition is completed, the reaction is refluxed at 60 - 65 °C for 3 - 4 h, then deionized water is added dropwise and the reaction continues for 3 - 4 h, and then the temperature is lowered to 20 - 25 °C and the reaction continues for 10 - 12 h. After the reaction is completed, it is centrifuged, washed, and vacuum dried to obtain the acrylic acid-modified chitosan; the reaction mass ratio of chitosan, triethylamine, glycidyl methacrylate, and deionized water is 3:10:(15 - 17):0.5.

[0018] Preferably, the preparation process of the acrylic acid-modified tannic acid is as follows: Tannic acid, ethyl acetate, and butyl acetate are mixed and heated to dissolve, then triphenylphosphine and hydroquinone are added, and after stirring evenly, glycidyl methacrylate is added dropwise, and the reaction is stirred at 95 - 100 °C for 25 - 30 h. After the reaction is completed, it is dried to obtain the acrylic acid-modified tannic acid; the reaction mass ratio of tannic acid and glycidyl methacrylate is 1.5:(4 - 5).

[0019] Preferably, the preparation process of the acrylated quaternary ammonium salt is as follows: Ethyl 2-(dimethylamino)ethyl acrylate and cetyl chloride are sequentially added to acetonitrile, and the mixture is stirred at 50-55 °C for 5-6 h. After the reaction, rotary evaporation and drying are carried out to obtain the acrylated quaternary ammonium salt; the reaction mass ratio of ethyl 2-(dimethylamino)ethyl acrylate to cetyl chloride is 16:(31-34).

[0020] The beneficial effects of the present invention are as follows:

[0021] The feature of the present invention is that in step one, the stainless steel plate is successively polished, ultrasonically cleaned, dried, laser-etched, and then cleaned to obtain a pretreated stainless steel plate. In this step, microscopic protrusions and depressions are formed on the stainless steel surface through laser etching. Therefore, when the coating operation is carried out subsequently, the coating material can penetrate into this rough structure, greatly increasing the contact area between the coating and the stainless steel plate surface, thereby significantly improving the mechanical interlocking force of the coating and making the coating adhere more firmly to the stainless steel plate. In addition, the coating material on the rough surface will not agglomerate or flow unevenly due to factors such as surface tension, thus ensuring the thickness uniformity and quality stability of the coating.

[0022] The feature of the present invention is that in step two, mesoporous polydopamine nanoparticles are added to Tris-HCl buffer solution to obtain a mesoporous polydopamine impregnating solution; then the pretreated stainless steel plate is immersed in the mesoporous polydopamine impregnating solution, and after a light-shielded reaction, an antibacterial adhesion layer is obtained. The antibacterial adhesion layer formed on the stainless steel plate surface usually has a micro-nano scale topological structure. There are many sharp protrusions and edges in these structures that are similar in size to or smaller than bacteria. Therefore, when bacteria adhere to the surface of this material, this micro-nano structure will directly contact the bacteria, generating extremely high local pressure and piercing the bacterial cell membrane, resulting in the death of bacteria. In addition, the polydopamine molecule contains a large number of functional groups such as catechol and amino groups. In the environment of Tris-HCl buffer solution, these functional groups can chemically react with the metal atoms on the surface of the pretreated stainless steel plate, enabling polydopamine to firmly adhere to the stainless steel plate surface and form a stable antibacterial adhesion layer. Therefore, the formed antibacterial adhesion layer has dual advantages. Good physical antibacterial properties can effectively inhibit the growth and reproduction of bacteria on the stainless steel plate surface, reducing bacterial contamination; while good adhesion ensures that the antibacterial layer can firmly adhere to the stainless steel plate and will not easily fall off, thereby prolonging the durability of the antibacterial effect and improving the antibacterial performance and service life of the stainless steel plate in various environments.

[0023] The characteristics of the present invention are as follows. In step three, vinyl-terminated polyurethane is prepared by adding polypropylene glycol, polycaprolactone diol, isophorone diisocyanate, and 2-hydroxyethyl methacrylate. Ring-opening reaction occurs by adding chitosan, triethylamine, and glycidyl methacrylate to obtain acrylic acid-modified chitosan. Ring-opening reaction occurs by adding tannic acid, glycidyl methacrylate, triphenylphosphine, and hydroquinone to obtain acrylic acid-modified tannic acid. Nucleophilic substitution reaction occurs by adding 2-(dimethylamino)ethyl methacrylate and hexadecyl chloride to obtain acrylated quaternary ammonium salt. Then, the three substances with both C=C and antibacterial structures (tannic acid antibacterial structure, chitosan antibacterial structure, quaternary ammonium salt antibacterial structure) and vinyl-terminated polyurethane are mixed and copolymerized under the initiation of the photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone to undergo photocuring to obtain the antibacterial layer.

[0024] The tannic acid antibacterial structure, chitosan antibacterial structure, and quaternary ammonium salt antibacterial structure in the antibacterial layer can play a synergistic antibacterial role. Different antibacterial components act on different targets of bacteria, and can more comprehensively destroy the physiological functions of bacteria. Among them, chitosan and quaternary ammonium salt mainly interact with the surface of bacteria through electrostatic action to destroy the cell membrane; while tannic acid can further bind to proteins and metal ions inside the cell to interfere with bacterial metabolism and gene expression; the antibacterial efficiency can be greatly improved and the antibacterial performance of the antibacterial layer can be enhanced through the multi-target action mode. In addition, during the photocuring process, vinyl-terminated polyurethane copolymerizes with acrylic acid-modified chitosan, acrylated quaternary ammonium salt, and acrylic acid-modified tannic acid to form a stable three-dimensional network structure, so the antibacterial components are fixed in this network structure and will not easily flow out. At the same time, this network structure can play a role in slowly releasing antibacterial components, enabling the antibacterial components to be continuously and slowly released into the surrounding environment to maintain a long-term antibacterial effect. Detailed implementation manners

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0026] Source of raw materials:

[0027] Pluronic F-127 is provided by Sigma-Aldrich; polypropylene glycol is provided by Nantong Renda Chemical Co., Ltd., with the model number PPG4000; polycaprolactone diol is provided by Hubei Darl Chemical Co., Ltd., with the model number Darl-1; chitosan, Mw = 200 kDa, and the degree of deacetylation is 85%.

[0028] Example 1: Step 1: The stainless steel alloy powder is successively subjected to encapsulation welding, forging, hot rolling, and forming processing to obtain a stainless steel plate; then the stainless steel plate is successively polished, ultrasonically cleaned, dried, laser etched, and cleaned again to obtain a pretreated stainless steel plate; Laser etching parameters: scanning power is 20W, scanning speed is 350mm / s, and scanning spacing is 40μm;

[0029] The content of each component of the stainless steel alloy powder is as follows: by mass fraction, C: 0.02%, B: 1%, Si: 0.6%, Mn 1.2%, P: 0.003%, S: 0.022%, Ni: 13%, Cr: 19%, N: 0.06%, O: 0.0035%, and the balance is Fe and unavoidable impurities;

[0030] Step 2: Pluronic F-127 and 1,3,5-trimethylbenzene are successively added to the ethanol aqueous solution, ultrasonically dispersed to obtain an emulsion, and then magnetically stirred for 40 min. Then, Tris-HCl aqueous solution and dopamine hydrochloride are successively added, and the pH is adjusted to 8.7. The reaction is carried out in the dark at 30°C for 30 h. After the reaction, solid nanoparticles are collected at 5°C, and then ultrasonically cleaned, centrifugally collected, washed with deionized water, and freeze-dried to obtain mesoporous polydopamine nanoparticles; The reaction mass ratio of Pluronic F-127, 1,3,5-trimethylbenzene, Tris-HCl, and dopamine hydrochloride is 38:36:9:6;

[0031] The mesoporous polydopamine nanoparticles are added to a Tris-HCl buffer solution with a pH of 9.0 to obtain a mesoporous polydopamine impregnating solution with a concentration of 5 mg / mL; then the pretreated stainless steel plate is impregnated in the mesoporous polydopamine impregnating solution, and the reaction is carried out in the dark at 30°C for 30 h to obtain an antibacterial adhesion layer;

[0032] Step 3: Under a nitrogen atmosphere, polypropylene glycol and polycaprolactone diol are mixed and stirred at 60°C for 30 min. Then, isophorone diisocyanate and dibutyltin dilaurate are added, and the temperature is raised to 95°C and stirring reaction is continued for 2.5 h. Then, the temperature is lowered to 50°C, and a capping agent, 2-hydroxyethyl methacrylate, is added and the reaction is continued for 3 h to obtain vinyl-capped polyurethane; When preparing vinyl-capped polyurethane, the reaction mass ratio of polypropylene glycol, polycaprolactone diol, isophorone diisocyanate, and 2-hydroxyethyl methacrylate is 3:1.3:2:1;

[0033] Chitosan and triethylamine were added to tetrahydrofuran. After thorough stirring, glycidyl methacrylate was added dropwise in sequence. After the addition was completed, the mixture was refluxed at 65 °C for 4 h, then deionized water was added dropwise and the reaction continued for 4 h. Then the temperature was lowered to 25 °C and the reaction continued for 12 h. After the reaction was completed, it was centrifuged, washed, and dried under vacuum to obtain acrylic acid-modified chitosan. The reaction mass ratio of chitosan, triethylamine, glycidyl methacrylate, and deionized water was 3:10:16:0.5;

[0034] Tannic acid, ethyl acetate, and butyl acetate were mixed and heated to dissolve. Then triphenylphosphine and hydroquinone were added. After stirring evenly, glycidyl methacrylate was added dropwise, and the mixture was stirred and reacted at 100 °C for 30 h. After the reaction was completed, it was dried to obtain acrylic acid-modified tannic acid. The reaction mass ratio of tannic acid and glycidyl methacrylate was 1.5:4.5;

[0035] 2-(Dimethylamino)ethyl methacrylate and hexadecyl chloride were added to acetonitrile in sequence and stirred and reacted at 55 °C for 6 h. After the reaction was completed, it was rotary evaporated and dried to obtain acrylated quaternary ammonium salt. The reaction mass ratio of 2-(dimethylamino)ethyl methacrylate and hexadecyl chloride was 16:32;

[0036] Then 62% vinyl-terminated polyurethane, 17% acrylic acid-modified chitosan, 12% acrylic acid-modified tannic acid, and 7% acrylated quaternary ammonium salt were mixed. After stirring evenly, 2% photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone was added and stirred in the dark for 20 min to obtain a polyurethane-acrylic antibacterial coating. The polyurethane-acrylic antibacterial coating was coated on the surface of the stainless steel plate obtained in Step 2 and photocured at a wavelength of 260 nm for 7 min to obtain an antibacterial layer with a thickness of 25 μm, which was the finished product.

[0037] Example 2: Step 1: The stainless steel alloy powder was encapsulated and welded, forged, hot-rolled, and formed in sequence to obtain a stainless steel plate. Then the stainless steel plate was ground, ultrasonically cleaned, dried, laser etched, and cleaned again to obtain a pretreated stainless steel plate. Laser etching parameters: scanning power was 17 W, scanning speed was 300 mm / s, and scanning pitch was 37 μm;

[0038] The component contents of the stainless steel alloy powder were as follows: by mass fraction, C: 0.02%, B: 1%, Si: 0.6%, Mn 1.2%, P: 0.003%, S: 0.022%, Ni: 13%, Cr: 19%, N: 0.06%, O: 0.0035%, and the balance was Fe and unavoidable impurities;

[0039] Step 2: Add Pluronic F-127 and 1,3,5-trimethylbenzene to the ethanol aqueous solution in sequence. After ultrasonic dispersion to obtain an emulsion, stir magnetically for 35 min, then add Tris-HCl aqueous solution and dopamine hydrochloride in sequence, and adjust the pH to 8.6. React at 27 °C in the dark for 27 h. After the reaction, collect the solid nanoparticles at 4 °C, and then through ultrasonic cleaning, centrifugal collection, washing with deionized water, and freeze-drying, mesoporous polydopamine nanoparticles are obtained; the reaction mass ratio of Pluronic F-127, 1,3,5-trimethylbenzene, Tris-HCl, and dopamine hydrochloride is 38:36:9:6;

[0040] Add the mesoporous polydopamine nanoparticles to a Tris-HCl buffer solution with a pH of 8.7 to obtain a mesoporous polydopamine impregnating solution with a concentration of 4 mg / mL; then immerse the pretreated stainless steel plate in the mesoporous polydopamine impregnating solution and react at 27 °C in the dark for 27 h to obtain an antibacterial adhesion layer;

[0041] Step 3: Under a nitrogen atmosphere, mix polypropylene glycol and polycaprolactone diol, stir at 57 °C for 25 min, then add isophorone diisocyanate and dibutyltin dilaurate, raise the temperature to 92 °C and continue stirring and reacting for 2.3 h, then cool down to 47 °C, and add the capping agent 2-hydroxyethyl methacrylate and continue reacting for 2.5 h to obtain vinyl-capped polyurethane; when preparing vinyl-capped polyurethane, the reaction mass ratio of polypropylene glycol, polycaprolactone diol, isophorone diisocyanate, and 2-hydroxyethyl methacrylate is 3:1.3:2:1;

[0042] Add chitosan and triethylamine to tetrahydrofuran, stir well and then dropwise add glycidyl methacrylate in sequence. After the addition is completed, reflux and react at 62 °C for 3.5 h, then dropwise add deionized water and continue reacting for 3.5 h, then cool down to 22 °C and continue reacting for 11 h. After the reaction, through centrifugation, washing, and vacuum drying, acrylic acid-modified chitosan is obtained; the reaction mass ratio of chitosan, triethylamine, glycidyl methacrylate, and deionized water is 3:10:16:0.5;

[0043] Mix tannic acid, ethyl acetate, and butyl acetate, heat and dissolve them, then add triphenylphosphine and hydroquinone, stir evenly and then dropwise add glycidyl methacrylate, and stir and react at 97 °C for 27 h. After the reaction, through drying, acrylic acid-modified tannic acid is obtained; the reaction mass ratio of tannic acid and glycidyl methacrylate is 1.5:4.5;

[0044] Add 2-(dimethylamino)ethyl methacrylate and hexadecyl chloride to acetonitrile in sequence, stir and react at 52 °C for 5.5 h. After the reaction, through rotary evaporation and drying, acrylated quaternary ammonium salt is obtained; the reaction mass ratio of 2-(dimethylamino)ethyl methacrylate and hexadecyl chloride is 16:32;

[0045] Then, 62% vinyl-terminated polyurethane, 17% acrylic acid-modified chitosan, 12% acrylic acid-modified tannic acid, and 7% acrylated quaternary ammonium salt are mixed. After stirring evenly, 2% photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone is added and stirred in the dark for 15 min to obtain a polyurethane-acrylic antibacterial coating. The polyurethane-acrylic antibacterial coating is coated on the surface of the stainless steel plate obtained in the second step and photocured at a wavelength of 255 nm for 6 min to obtain an antibacterial layer with a thickness of 25 μm, which is the finished product.

[0046] Example 3: Step 1: The stainless steel alloy powder is successively subjected to encapsulation welding, forging, hot rolling, and forming processing to obtain a stainless steel plate. Then, the stainless steel plate is successively polished, ultrasonically cleaned, dried, laser etched, and cleaned again to obtain a pretreated stainless steel plate. Laser etching parameters: scanning power is 15 W, scanning speed is 250 mm / s, and scanning spacing is 35 μm.

[0047] The component contents of the stainless steel alloy powder are as follows: by mass fraction, C: 0.02%, B: 1%, Si: 0.6%, Mn 1.2%, P: 0.003%, S: 0.022%, Ni: 13%, Cr: 19%, N: 0.06%, O: 0.0035%, and the balance is Fe and unavoidable impurities.

[0048] Step 2: Pluronic F-127 and 1,3,5-trimethylbenzene are successively added to the ethanol aqueous solution. After ultrasonic dispersion to obtain an emulsion, magnetic stirring is carried out for 30 min. Then, Tris-HCl aqueous solution and dopamine hydrochloride are successively added, and the pH is adjusted to 8.5. The reaction is carried out in the dark at 25 °C for 25 h. After the reaction is completed, solid nanoparticles are collected at 3 °C, and then ultrasonically cleaned, centrifugally collected, washed with deionized water, and freeze-dried to obtain mesoporous polydopamine nanoparticles. The reaction mass ratio of Pluronic F-127, 1,3,5-trimethylbenzene, Tris-HCl, and dopamine hydrochloride is 38:36:9:6.

[0049] The mesoporous polydopamine nanoparticles are added to a Tris-HCl buffer solution with a pH of 8.5 to obtain a mesoporous polydopamine impregnation solution with a concentration of 3 mg / mL. Then, the pretreated stainless steel plate is impregnated in the mesoporous polydopamine impregnation solution, and the reaction is carried out in the dark at 25 °C for 25 h to obtain an antibacterial adhesion layer.

[0050] Step 3: Under a nitrogen atmosphere, mix polypropylene glycol and polycaprolactone diol, stir at 55°C for 20 min, then add isophorone diisocyanate and dibutyltin dilaurate, raise the temperature to 90°C and continue stirring and reacting for 2 h, then cool down to 45°C, and add the capping agent 2-hydroxyethyl methacrylate and continue reacting for 2 h to obtain vinyl-capped polyurethane; when preparing vinyl-capped polyurethane, the reaction mass ratio of polypropylene glycol, polycaprolactone diol, isophorone diisocyanate, and 2-hydroxyethyl methacrylate is 3:1.3:2:1;

[0051] Add chitosan and triethylamine to tetrahydrofuran, stir well and then dropwise add glycidyl methacrylate in sequence. After the addition is completed, reflux and react at 60°C for 3 h, then dropwise add deionized water and continue reacting for 3 h, then cool down to 20°C and continue reacting for 10 h. After the reaction is completed, centrifuge, wash, and vacuum dry to obtain acrylic acid-modified chitosan; among them, the reaction mass ratio of chitosan, triethylamine, glycidyl methacrylate, and deionized water is 3:10:16:0.5;

[0052] Mix tannic acid, ethyl acetate, and butyl acetate, heat and dissolve, then add triphenylphosphine and hydroquinone, stir evenly and then dropwise add glycidyl methacrylate, stir and react at 95°C for 25 h, and after the reaction is completed, dry to obtain acrylic acid-modified tannic acid; among them, the reaction mass ratio of tannic acid and glycidyl methacrylate is 1.5:4.5;

[0053] Add 2-(dimethylamino)ethyl methacrylate and hexadecyl chloride to acetonitrile in sequence, stir and react at 50°C for 5 h, and after the reaction is completed, carry out rotary evaporation and drying to obtain acrylated quaternary ammonium salt; among them, the reaction mass ratio of 2-(dimethylamino)ethyl methacrylate and hexadecyl chloride is 16:32;

[0054] Then mix 62% vinyl-capped polyurethane, 17% acrylic acid-modified chitosan, 12% acrylic acid-modified tannic acid, and 7% acrylated quaternary ammonium salt, stir evenly, add 2% photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone, and stir in the dark for 10 min to obtain a polyurethane-acrylic antibacterial coating; coat the polyurethane-acrylic antibacterial coating on the surface of the stainless steel plate obtained in Step 2, and photocure at a wavelength of 250 nm for 5 min to obtain an antibacterial layer with a thickness of 25 μm, which is the finished product.

[0055] Comparative Example 1: Remove the pretreatment of the stainless steel plate, and the rest is the same as in Example 1. The specific steps are as follows: Step 1: Perform encapsulation welding, forging, hot rolling, and forming processing on the stainless steel alloy powder in sequence to obtain a stainless steel plate;

[0056] The contents of the stainless steel alloy powder are as follows: by mass fraction, C: 0.02%, B: 1%, Si: 0.6%, Mn 1.2%, P: 0.003%, S: 0.022%, Ni: 13%, Cr: 19%, N: 0.06%, O: 0.0035%, and the balance is Fe and unavoidable impurities;

[0057] Step 2: Pluronic F-127 and 1,3,5-trimethylbenzene are sequentially added to an ethanol aqueous solution, ultrasonically dispersed to obtain an emulsion, and then magnetically stirred for 40 minutes. Tris-HCl aqueous solution and dopamine hydrochloride are then added in sequence, and the pH is adjusted to 8.7. The mixture is reacted at 30°C in the dark for 30 hours. After the reaction is completed, solid nanoparticles are collected at 5°C, ultrasonically cleaned, centrifuged, washed with deionized water, and freeze-dried to obtain mesoporous polydopamine nanoparticles. The reaction mass ratio of Pluronic F-127, 1,3,5-trimethylbenzene, Tris-HCl, and dopamine hydrochloride is 38:36:9:6.

[0058] Mesoporous polydopamine nanoparticles were added to a Tris-HCl buffer solution with a pH of 9.0 to obtain a mesoporous polydopamine impregnation solution with a concentration of 5 mg / mL; a stainless steel plate was then immersed in the mesoporous polydopamine impregnation solution and reacted at 30°C in the dark for 30 hours to obtain an antibacterial adhesion layer;

[0059] Step 3: Under a nitrogen environment, polypropylene glycol and polycaprolactone diol are mixed, stirred at 60°C for 30 minutes, and then isophorone diisocyanate and dibutyltin dilaurate are added, the temperature is raised to 95°C and the stirring reaction is continued for 2.5 hours, and then the temperature is lowered to 50°C, and the blocking agent hydroxyethyl methacrylate is added and the reaction is continued for 3 hours to obtain a vinyl-terminated polyurethane; when preparing the vinyl-terminated polyurethane, the reaction mass ratio of polypropylene glycol, polycaprolactone diol, isophorone diisocyanate, and hydroxyethyl methacrylate is 3:1.3:2:1;

[0060] Chitosan and triethylamine were added to tetrahydrofuran, and glycidyl methacrylate was added dropwise in sequence after thorough stirring. After the addition was completed, the mixture was refluxed at 65°C for 4 hours, and deionized water was added dropwise to continue the reaction for 4 hours. The mixture was then cooled to 25°C and continued to react for 12 hours. After the reaction was completed, the mixture was centrifuged, washed, and vacuum-dried to obtain acrylic acid-modified chitosan. The reaction mass ratio of chitosan, triethylamine, glycidyl methacrylate, and deionized water was 3:10:16:0.5.

[0061] Mix tannic acid, ethyl acetate, and butyl acetate, heat and dissolve them, then add triphenylphosphine and hydroquinone. After stirring evenly, dropwise add glycidyl methacrylate, and stir and react at 100 °C for 30 h. After the reaction is completed, dry to obtain acrylic acid-modified tannic acid; the reaction mass ratio of tannic acid to glycidyl methacrylate is 1.5:4.5;

[0062] Add ethyl 2-dimethylaminomethacrylate and hexadecyl chloride to acetonitrile in sequence, stir and react at 55 °C for 6 h. After the reaction is completed, carry out rotary evaporation and drying to obtain acrylated quaternary ammonium salt; the reaction mass ratio of ethyl 2-dimethylaminomethacrylate to hexadecyl chloride is 16:32;

[0063] Then mix 62% vinyl-terminated polyurethane, 17% acrylic acid-modified chitosan, 12% acrylic acid-modified tannic acid, and 7% acrylated quaternary ammonium salt, stir evenly, add 2% photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone, and stir in the dark for 20 min to obtain a polyurethane-acrylic antibacterial coating; coat the polyurethane-acrylic antibacterial coating on the surface of the stainless steel plate obtained in Step 2, and photocure at a wavelength of 260 nm for 7 min to obtain an antibacterial layer with a thickness of 25 μm, which is the finished product.

[0064] Comparative Example 2: Remove the antibacterial adhesion layer, and the rest is the same as in Example 1. The specific steps are as follows: Step 1: Encapsulate and weld, forge, hot-roll, and form stainless steel alloy powder in sequence to obtain a stainless steel plate; then polish, ultrasonically clean, dry, laser etch, and clean the stainless steel plate again to obtain a pretreated stainless steel plate; Laser etching parameters: scanning power is 20 W, scanning speed is 350 mm / s, and scanning spacing is 40 μm;

[0065] The component contents of the stainless steel alloy powder are: by mass fraction, C: 0.02%, B: 1%, Si: 0.6%, Mn 1.2%, P: 0.003%, S: 0.022%, Ni: 13%, Cr: 19%, N: 0.06%, O: 0.0035%, and the balance is Fe and unavoidable impurities;

[0066] Step 2: Under a nitrogen atmosphere, mix polypropylene glycol and polycaprolactone diol, stir at 60 °C for 30 min, then add isophorone diisocyanate and dibutyltin dilaurate, raise the temperature to 95 °C and continue to stir and react for 2.5 h, then cool down to 50 °C, and add the terminator 2-hydroxyethyl methacrylate and continue to react for 3 h to obtain vinyl-terminated polyurethane; when preparing vinyl-terminated polyurethane, the reaction mass ratio of polypropylene glycol, polycaprolactone diol, isophorone diisocyanate, and 2-hydroxyethyl methacrylate is 3:1.3:2:1;

[0067] Chitosan and triethylamine were added to tetrahydrofuran. After stirring well, glycidyl methacrylate was added dropwise successively. After the addition was completed, the mixture was refluxed at 65 °C for 4 h, then deionized water was added dropwise and the reaction continued for 4 h. Subsequently, the temperature was lowered to 25 °C and the reaction continued for 12 h. After the reaction was completed, it was centrifuged, washed, and dried under vacuum to obtain acrylic acid-modified chitosan. The reaction mass ratio of chitosan, triethylamine, glycidyl methacrylate, and deionized water was 3:10:16:0.5;

[0068] Tannic acid, ethyl acetate, and butyl acetate were mixed and heated to dissolve. Then triphenylphosphine and hydroquinone were added. After stirring evenly, glycidyl methacrylate was added dropwise and the mixture was stirred and reacted at 100 °C for 30 h. After the reaction was completed, it was dried to obtain acrylic acid-modified tannic acid. The reaction mass ratio of tannic acid and glycidyl methacrylate was 1.5:4.5;

[0069] 2-(Dimethylamino)ethyl methacrylate and hexadecyl chloride were added to acetonitrile successively and stirred and reacted at 55 °C for 6 h. After the reaction was completed, it was rotary evaporated and dried to obtain acrylated quaternary ammonium salt. The reaction mass ratio of 2-(dimethylamino)ethyl methacrylate and hexadecyl chloride was 16:32;

[0070] Then 62% vinyl-terminated polyurethane, 17% acrylic acid-modified chitosan, 12% acrylic acid-modified tannic acid, and 7% acrylated quaternary ammonium salt were mixed. After stirring evenly, 2% photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone was added and stirred in the dark for 20 min to obtain a polyurethane-acrylic antibacterial coating. The polyurethane-acrylic antibacterial coating was coated on the surface of a pretreated stainless steel plate and photocured at a wavelength of 260 nm for 7 min to obtain an antibacterial layer with a thickness of 25 μm, which was the finished product.

[0071] Comparative Example 3: The antibacterial layer was removed, and the rest was the same as in Example 1. The specific steps were as follows: Step 1: The stainless steel alloy powder was encapsulated and welded, forged, hot-rolled, and formed successively to obtain a stainless steel plate. Then the stainless steel plate was polished, ultrasonically cleaned, dried, laser etched, and cleaned again to obtain a pretreated stainless steel plate. Laser etching parameters: scanning power was 20 W, scanning speed was 350 mm / s, and scanning pitch was 40 μm;

[0072] The component contents of the stainless steel alloy powder were as follows: by mass fraction, C: 0.02%, B: 1%, Si: 0.6%, Mn 1.2%, P: 0.003%, S: 0.022%, Ni: 13%, Cr: 19%, N: 0.06%, O: 0.0035%, and the balance was Fe and unavoidable impurities;

[0073] Step 2: Add Pluronic F-127 and 1,3,5-trimethylbenzene to the ethanol aqueous solution in sequence. After ultrasonic dispersion to obtain an emulsion, stir magnetically for 40 min. Then add Tris-HCl aqueous solution and dopamine hydrochloride in sequence, and adjust the pH to 8.7. React at 30 °C in the dark for 30 h. After the reaction, collect the solid nanoparticles at 5 °C, and then perform ultrasonic cleaning, centrifugal collection, washing with deionized water, and freeze-drying to obtain mesoporous polydopamine nanoparticles; the reaction mass ratio of Pluronic F-127, 1,3,5-trimethylbenzene, Tris-HCl, and dopamine hydrochloride is 38:36:9:6;

[0074] Add the mesoporous polydopamine nanoparticles to the Tris-HCl buffer solution with a pH of 9.0 to obtain a mesoporous polydopamine impregnating solution with a concentration of 5 mg / mL; then immerse the pretreated stainless steel plate in the mesoporous polydopamine impregnating solution and react at 30 °C in the dark for 30 h to obtain an antibacterial adhesion layer, which is the finished product.

[0075] Detection test:

[0076] Antibacterial performance test: Drop the Escherichia coli suspension (concentration of 1×10 8 CFU / mL) onto the surface of the finished product prepared by the present invention, and then press with a sterile glass slide to evenly spread the Escherichia coli suspension on the surface of the finished product. Incubate at 30 - 40 °C for 2 h. Then rinse the surface of the finished product and the glass slide with PBS phosphate buffer solution, dilute the rinsed Escherichia coli suspension by 10 times, inoculate it into the agar medium, incubate at 30 - 40 °C for 20 - 24 h, and then count the number of colonies. Set a control group, use a stainless steel plate without any treatment, repeat the above steps, count the number of colonies again, and substitute the data of the experimental group and the control group into the formula to calculate the antibacterial rate.

[0077] Adhesion test: Take the finished product prepared by the present invention as the test object, and perform a pull-out test using an electronic universal testing machine to test the adhesion strength between the coating and the substrate. The results are as follows in the table:

[0078] Antibacterial rate / % <![CDATA[Adhesion strength / MPa > Example 1 98.7 3.7 Example 2 98.5 3.7 Example 3 98.3 3.6 Comparative Example 1 94.7 3.3 Comparative Example 2 83.8 2.6 Comparative Example 3 77.9 3.1

[0079] Conclusion: The dosages in Examples 1 - 3 remain unchanged, and only some reaction parameters are modified. From the experimental data, it can be seen that there are no obvious fluctuations in the performance of the samples.

[0080] Comparative Example 1: The pretreatment of the stainless steel plate was removed, and the rest was the same as in Example 1. It can be seen from the experimental data that, compared with Example 1, the adhesion strength decreased to 3.3 MPa. The reason for the analysis is that the pretreatment step of the stainless steel plate forms a rough surface, thus greatly increasing the contact area between the coating and the surface of the stainless steel plate, thereby significantly improving the mechanical interlocking force of the coating and making the coating adhere more firmly to the stainless steel plate. Therefore, the adhesion strength decreased after it was removed.

[0081] Comparative Example 2: The antibacterial adhesion layer was removed, and the rest was the same as in Example 1. It can be seen from the experimental data that, compared with Example 1, the antibacterial rate decreased to 83.8%, and the adhesion strength decreased to 2.6 MPa. The reason for the analysis is that the mesoporous polydopamine nanostructure of the antibacterial adhesion layer has good physical antibacterial properties, can effectively inhibit the growth and reproduction of bacteria on the surface of the stainless steel plate, and also has good adhesion and is not easy to fall off. Therefore, the antibacterial rate increased and the adhesion strength decreased after it was removed.

[0082] Comparative Example 3: The antibacterial layer was removed, and the rest was the same as in Example 1. It can be seen from the experimental data that, compared with Example 1, the antibacterial rate decreased to 77.9%, and the adhesion strength decreased to 3.1 MPa. The reason for the analysis is that the antibacterial layer contains a stable three-dimensional network structure formed by various antibacterial structures, so it has both excellent antibacterial effects and antibacterial stability. Therefore, the antibacterial rate decreased after it was removed.

[0083] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "including", "comprising" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0084] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of an antibacterial stainless steel plate for a refrigerator liner, characterized in that: It includes the following steps: Step 1: The stainless steel alloy powder is successively subjected to encapsulation welding, forging, hot rolling, and forming processing to obtain a stainless steel plate; then the stainless steel plate is successively polished, ultrasonically cleaned, dried, laser etched, and cleaned again to obtain a pretreated stainless steel plate; Step 2: Mesoporous polydopamine nanoparticles are added to a Tris-HCl buffer solution with a pH of 8.5 - 9.0 to obtain a mesoporous polydopamine impregnating solution with a concentration of 3 - 5 mg / mL; then the pretreated stainless steel plate is impregnated in the mesoporous polydopamine impregnating solution, and reacted at 25 - 30 °C in the dark for 25 - 30 h to obtain an antibacterial adhesion layer; Step 3: Under a nitrogen atmosphere, polypropylene glycol and polycaprolactone diol are mixed and stirred at 55 - 60 °C for 20 - 30 min, then isophorone diisocyanate and dibutyltin dilaurate are added, the temperature is raised to 90 - 95 °C and stirring reaction continues for 2.0 - 2.5 h, then the temperature is lowered to 45 - 50 °C, and a capping agent 2-hydroxyethyl methacrylate is added and reaction continues for 2 - 3 h to obtain vinyl-capped polyurethane; then vinyl-capped polyurethane, acrylic acid-modified chitosan, acrylic acid-modified tannic acid, and acrylated quaternary ammonium salt are mixed, and after stirring evenly, a photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone is added and stirred in the dark for 10 - 20 min to obtain a polyurethane-acrylic antibacterial coating; the polyurethane-acrylic antibacterial coating is coated on the surface of the stainless steel plate obtained in Step 2 and photocured at a wavelength of 250 - 260 nm for 5 - 7 min to obtain an antibacterial layer, which is the finished product.

2. The preparation method of an antibacterial stainless steel plate for a refrigerator inner liner according to claim 1, characterized in that: In Step 1, the laser etching parameters are: the scanning power is 15 - 20 W, the scanning speed is 250 - 350 mm / s, and the scanning pitch is 35 - 40 μm.

3. The preparation method of an antibacterial stainless steel plate for a refrigerator liner according to claim 1, characterized in that: In Step 1, the component contents of the stainless steel alloy powder are: by mass fraction, C: 0.01 - 0.08%, B: 0.5 - 1.5%, Si: 0.5 - 0.7%, Mn 1.0 - 1.5%, P: 0.0025 - 0.035%, S: 0.020 - 0.025%, Ni: 12.0 - 15.0%, Cr: 18.0 - 20.0%, N: 0.05 - 0.07%, O: 0.003 - 0.004%, and the balance is Fe and unavoidable impurities.

4. The preparation method of an antibacterial stainless steel plate for a refrigerator liner according to claim 1, characterized in that: In Step 2, the preparation process of the mesoporous polydopamine nanoparticles is: Pluronic F-127 and 1,3,5-trimethylbenzene are successively added to an ethanol aqueous solution, ultrasonically dispersed to obtain an emulsion and then magnetically stirred for 30 - 40 min, then a Tris-HCl aqueous solution and dopamine hydrochloride are successively added, and the pH is adjusted to 8.5 - 8.7, and reacted at 25 - 30 °C in the dark for 25 - 30 h. After the reaction, solid nanoparticles are collected at 3 - 5 °C, and then ultrasonically cleaned, centrifugally collected, washed with deionized water, and freeze-dried to obtain mesoporous polydopamine nanoparticles.

5. The preparation method of an antibacterial stainless steel plate for a refrigerator liner according to claim 4, characterized in that: The reaction mass ratio of Pluronic F-127, 1,3,5-trimethylbenzene, Tris-HCl, and dopamine hydrochloride is (37 - 40):36:9:

6.

6. The preparation method of an antibacterial stainless steel plate for a refrigerator liner according to claim 1, characterized in that: In Step 3, when preparing vinyl-terminated polyurethane, the reaction mass ratio of polypropylene glycol, polycaprolactone diol, isophorone diisocyanate, and 2-hydroxyethyl methacrylate is 3: (1.0-1.6)：2：1。 7. The preparation method of an antibacterial stainless steel plate for a refrigerator liner according to claim 1, characterized in that: In Step 3, the component contents of the polyurethane-acrylic antibacterial coating are as follows: by mass fraction, 60-70% vinyl-terminated polyurethane, 15-20% acrylic acid-modified chitosan, 10-15% acrylated quaternary ammonium salt, 6-10% acrylic acid-modified tannic acid, and the balance is the photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone; the coating thickness is 20-30 μm.

8. The preparation method of an antibacterial stainless steel plate for a refrigerator liner according to claim 7, characterized in that: The preparation process of acrylic acid-modified chitosan is as follows: Add chitosan and triethylamine to tetrahydrofuran, stir well and then dropwise add glycidyl methacrylate in sequence. After the addition is completed, reflux and react at 60-65 °C for 3-4 h, then dropwise add deionized water and continue to react for 3-4 h, and then cool down to 20-25 °C and continue to react for 10-12 h. After the reaction is completed, centrifuge, wash, and vacuum dry to obtain acrylic acid-modified chitosan; the reaction mass ratio of chitosan, triethylamine, glycidyl methacrylate, and deionized water is 3:10:(15-17):0.

5.

9. The preparation method of an antibacterial stainless steel plate for a refrigerator liner according to claim 7, characterized in that: The preparation process of acrylic acid-modified tannic acid is as follows: Mix tannic acid, ethyl acetate, and butyl acetate, heat and dissolve, then add triphenylphosphine and hydroquinone, stir evenly and then dropwise add glycidyl methacrylate, and stir and react at 95-100 °C for 25-30 h. After the reaction is completed, dry to obtain acrylic acid-modified tannic acid; the reaction mass ratio of tannic acid and glycidyl methacrylate is 1.5:(4-5).

10. The preparation method of an antibacterial stainless steel plate for a refrigerator liner according to claim 7, characterized in that: The preparation process of acrylated quaternary ammonium salt is as follows: Add 2-(dimethylamino)ethyl methacrylate and hexadecyl chloride to acetonitrile in sequence, stir and react at 50-55 °C for 5-6 h. After the reaction is completed, carry out rotary evaporation and drying to obtain acrylated quaternary ammonium salt; the reaction mass ratio of 2-(dimethylamino)ethyl methacrylate and hexadecyl chloride is 16:(31-34).